Our invention relates to a disabling circuit for a radio transmitter, and particularly to such a disabling circuit that disables the transmitter after a predetermined time period of continuous operation of the radio transmitter, and that requires a technician to restore the transmitter to operation.
In a typical mobile radio communication system, there is a fixed base station and a number of mobile stations which operate on an assigned radio channel. Such systems are very important to a number of services, one of which is a taxicab service. A taxicab service relies on a dispatcher at the base station receiving telephone calls from people who desire the cab service. In response to such a telephone call, the dispatcher will then transmit a request by radio to one of his taxicabs to respond to the customer who calls. Unfortunately, the dispatcher may not know the location of his taxicabs, or may have a preference for one of the taxicab drivers over another taxicab driver. In any case, if a taxicab driver feels that he is getting less service calls than he deserves or should get, he may key (or turn on) his radio transmitter for a long period of time, but not talk into his microphone. In a frequency modulation system, this effectively prevents any calls from being transmitted on the assigned radio channel, with the result that no one sends or receives messages, and the taxicab service becomes inefficient or even useless. However, the driver does not talk and thus remains anonymous.
Accordingly, a primary object of our invention is to provide a new and improved circuit that disables a radio transmitter after it has been continuously operated for longer than a predetermined time.
Another object of our invention is to provide a new and improved circuit that disables but does not damage a radio transmitter which is continuously keyed for an excessive period of time.
While it is desirable to prevent intentional or willful interference, it is also desirable that the taxicab company be able to restore the radio transmitter after it is disabled, and to also be able to know which taxicab driver caused the interference which resulted in the disabling of the radio transmitter.
Accordingly, another object of our invention is to provide a new and improved circuit that disables a radio transmitter which is continuously operated longer than a predetermined time, and which requires a licensed technician or serviceman having knowledge of the radio transmitter to restore the transmitter to operation.